Hi, it's the OP here - back to personal experience ...
I do hark back to the heady days of the late 60's when I used to just get the bike out of the shed, and hop onto it and cycle from my home in east Birmingham out to Tamworth, or Fillongley, or to watch the planes at Elmdon Airport as it was then just clad in my normal shoes, trousers and shirt, with a cape in my saddlebag in case it rained. I'll call this "Shirtsleeves" mode.
Then later, on my shiny Raleigh sports bike bought with my first pay packets - same thing, except to work each day and out at weekends.
While I did succumb to the classic "car pulling across in front of me and into the back of it I went", close shaves were rare and as I recollect I had only a handful - in total in several years! Car drivers and cyclists were all just people on the road.
Fast forward to the early 90's. Took up cycling again to regain some fitness. By then I'd been through the motorbike phase (when I found at first hand that bonedomes were a good idea, let alone compulsory) and the seat belt thing had become so obvious that I fitted them to my old bangers even before they were compulsory. Cycling helmets had appeared by then, so it was only natural to wear one. For which I was very grateful.
For suddenly I was banging my head on overhanging branches on country lanes. Such things didn't seem to exit in my yoof, and neither did the overhanging head-height door mirrors on trucks, on which I banged my head as I sat upright having stopped at a red light, just as a lorry pulled up beside me! By then I'd already discovered the joys of delayed-concussion-from-a-bang-on-the-head so I was happy to escape that one, thank you!
But even then I was quite happy to commute long the main Bristol road into my office central Birmingham during the rush hour from time to time until I had to move jobs in the mid 90's.
Fast forward again about 12 years, during which time my riding in Brum had been just Saturday afternoons across into Selly Oak,or the MAC for to meet up fr the occasional club evening ride. Still in Shirtsleeves mode, plus a helmet.
Now I'm getting more close shaves - a handful each month, then each week, - then on each ride. Finally ended up getting shaved too closely and thankful for getting off lightly (and for landing handily in the roadway outside the fire station!). Big bruises on the various "contact points" under soft clothing, hardly a mark under the contact point under a not-so-soft helmet.
So now I still have a hat, but take care to wear light-coloured shirts, and/or hi-viz, - and a bikecam in case I get walloped by another t**-**g who decides to bend the truth to take advantage of will-o-the-wisp witnesses. And I use bike paths more. And pavements.
And like BC (and someone from Spa Cycles I think it was in a magazine a few months back) I want to go back to the shirtsleeves approach to cycling.
But we aren't there yet, so I don't mind expressing my preferences for wearing a helmet for most of my riding 'cos I have personal experience of the benefits, even though I'd rather not have to. I want to enjoy my cycling for a while yet, and I don't want my wife to enjoy having to care me 'cos I couldn't be bothered with a little caution.
After all, that's why I fitted those seatbelts (and yes, they worked too).
Brompton, Condor Heritage, creaky joints and thinning white (formerly grey) hair
""You know you're getting old when it's easier to ride a bike than to get on and off it" - quote from observant jogger !